Cal. BPC § 5037

(a) All statements, records, schedules, working papers and memoranda made by a licensee or a partner, shareholder, officer, director, or employee of a licensee, incident to, or in the course of, rendering services to a client in the practice of public accountancy, except the reports submitted by the licensee to the client and except for records that are part of the client’s records, shall be and remain the property of the licensee in the absence of an express agreement between the licensee and the client to the contrary. No such statement, record, schedule, working paper, or memoranda shall be sold, transferred, or bequeathed, without the consent of the client or their personal representative or assignee, to anyone other than one or more surviving partners or stockholders or new partners or stockholders of the licensee, or any combined or merged firm or successor in interest to the licensee.

(b) A licensee shall furnish to their client or former client, upon request and reasonable notice:

(1) A copy of the licensee’s working papers, to the extent that those working papers include records that would ordinarily constitute part of the client’s records and are not otherwise available to the client.

(2) Any accounting or other records belonging to, or obtained from or on behalf of, the client that the licensee removed from the client’s premises or received for the client’s account. The licensee may make and retain copies of documents of the client when they form the basis for work done by them.